H Klym, I Hadzaman, O Shpotyuk - Multifunctional spinel-type ceramics for environment sensors - страница 1

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ВІСНИК ЛЬВІВ. УН-ТУ

Серія фіз. 2009. Bun. 43. С. 185-191

VISNYKLVIV UNIV. Ser. Physics. 2009. Is. 43. P. 185-191

УДК 53.093; 53.096

PACS number(s): 81.05 Je; 07.07. Df

MULTIFUNCTIONAL SPINEL-TYPE CERAMICS FOR ENVIRONMENT SENSORS

H. Klym1'2, I. Hadzaman1, O. Shpotyuk1, M. Brunner3, V. Balitska14

1Lviv Institute of Materials of SRC "Carat" 202, Stryjska str., 79031 Lviv, Ukraine

e-mail: shpotyuk@novas.lviv.ua 2Lviv Polytechnic National University 12, Bandera str., 79013 Lviv, Ukraine 3Fachhochschule Koln / University of Applied Sciences 2, Betzdorfer Strasse, 50679 Koln, Germany 4Lviv State University of Vital Activity Safety 35, Kleparivska str., 79007 Lviv, Ukraine

Temperature and humidity sensitive thick-film elements based on spinel-type NiMn2O4-CuMn2O4-MnCo2O4 manganites with p- and n-types of electrical conductivity and dielectric magnesium aluminate MgAl2O4 were prepared. These elements are shown to be successfully applied for integrated temperature/humidity sensors of environment monitoring and control.

Key words: spinel, thick-film, sensor, multilayer structure.

Spinel-type ceramics based on mixed transition-metal manganites and/or magnesium aluminates are known to be widely used for temperature measurement, in­rush current limiting, liquid and gas sensing, flow rate monitoring and indication etc. [1-5]. But their sensing functionality is sufficiently restricted because of bulk performance allowing, as a rule, no more than one kind of application. The aim of this work is to develop the high-reliable multifunctional sensors based on the above spinel-type compounds, allowing integrated temperature-humidity sensitivity for effective environment monitoring and control.

At the present time, a number of important problems connected with hybrid microelectronic circuits, multilayer ceramic circuits, temperature sensors, thermal stabilizers, etc. requires such resolution, when not bulk (e.g. sintered as typical bulk ceramics), but only thick-film performance of electrical components (possessing the possibility to group-technology route) is needed [5]. The well-known advantages of screen printing technology revealed in high reproducibility, flexibility, attainment of high reliability by glass coating as well as excellent accuracy, yield and interchangeability by functional trimming are expected to be very attractive now, for new-generation sensing electronics [6]. No less important is the factor of miniaturization for developed thick-film elements and systems, realized in a variety of their possible geometrical configurations. Thus, the development of high-reliable nanostructured thick films and their multilayers based on spinel-type compounds for multifunctional

© Klym H., Hadzaman I., Shpotyuk O., Brunner M. et al., 2009

environment sensors operating as simultaneous negative temperature coefficient thermistors and integrated temperature-humidity sensors are very important task [6-8].

To fabricate the integrated temperature-humidity thick-film sensors, only two principal approaches have been utilized, they being grounded on temperature dependence of electrical resistance for humidity-sensitive thick films and/or on humidity dependence of electrical resistance for temperature-sensitive thick films.

The first approach was typically applied to perovsite-type thick films like to BaTiO3 [9]. Within second approach grounded on spinel-type ceramics of mixed Mn-Co-Ni system with RuO2 additives, it was shown that temperature-sensitive elements in thick-film performance attain additionally good humidity sensitivity [10]. Despite improved long-term stability and temperature-sensitive properties with character material B constant value at the level of 3000 K, such thick-film elements possess only small humidity sensitivity. This disadvantage occurred because of relatively poor intrinsic pore topology proper to semiconducting mixed transition-metal manganited in contrast to dielectric aluminates with the same spinel-type structure.

Thick-film performance of mixed spinel-type manganites restricted by NiMn2O4-CuMn2O4-MnCo2O4 concentration triangle has a number of essential advantages, non-available for other ceramic composites. Within the above system, can be prepare the fine-grained semiconductor materials possessing p- (Cu01Ni01Mn12Co16O4) and n-type of electrical conductivity (Cu01Ni08Mn19Co02O4). So, a real possibility to prepare multilayer thick-film spinel-type structures for principally new device application, such as temperature-sensitive p-n-type diode junctions (thermoelectric transformers in a power supply, high-accurate temperature sensors and compensators exploring current-voltage dependence, thick-film diode structures, temperature difference detecting elements utilizing thermoelectromotive force, etc.) seems to be a quite realistic one. In addition, the prepared multilayer thick-film structures involving semiconductor NiMn2O4-CuMn2O4-MnCo2O4 and dielectric MgAl2O4 spinels can be potentially used as simultaneous thermistors and integrated temperature-humidity sensors with extremely rich range of exploitation properties.

The aim of this work is development and selection the high-reliable separate temperature and humidity sensitive thick-film elements based on spinel-type ceramics for multifunctional application in integrated temperature/humidity sensors.

Bulk temperature sensitive ceramics were prepared by a conventional ceramics processing route using reagent grade cooper carbonate hydroxide and nickel (cobalt) carbonate hydroxide hydrates [11]. Chemical composition of these ceramics and the main points in their sintering schedules are presented in table 1.

Table 1

Characteristics of temperature sensitive bulk ceramics

Chemical composition

Sintering temperature/duration

Phase composition

B25/85,

K

Cu0,1Ni0,1Co1,6MnuO4

1040 °C/ 4 h

spinel

3540

Cu0,1Ni0,8Co0,2Mn1,9O4

920 °C/8 h + 1200 °C/1 h +920 °C/24 h

spinel + NiO (11,5 %)

3378

The bulk MgAl2O4 ceramics were prepared via conventional sintering route as was described in more details elsewhere [12, 13]. The pellets were sintered in a special

regime with maximal temperature Ts 1 300 °C during 5 h. In a result, the humidity-sensitive ceramics with a so-called trimodal pore size distribution and character values of pore radiuses centered near -2,5, 85 and 450 nm and surface area near 6,93 m3/g were obtained.

Temperature sensitive Cu0)1Ni01Co1)6Mn12O4/Cu0)1Ni08Co0)2Mn19O4-based and humidity sensitive MgAl2O4-based pastes were prepared by mixing powders of basic ceramics (sintered bulk ceramics were preliminary destroyed, wet-milled and dried) with ecological glass powders (without PbO), inorganic binder Bi2O3 and organic vehicle (see table 2).

Table 2

Composition of temperature/humidity sensitive pastes

Constituents

Content, % mass

 

Cu0,1Ni0,1Co1,6MnuO4/ Cu01Ni08Co02Mn19O4-based paste

MgAl2O4-based paste

Basic ceramics

72,8

58

Bi2O3

2,9

4

Ecological glass

2,9

8

Organic vehicle

21,4

30

The prepared paste were printed on alumina substrates (Rubalit 708 S) with Ag-Pt electrodes using a using a manual screen-printing device equipped with a steel screen. Then, thick films were fired in furnace PEO-601-084. The typical planar type of design of the prepared films was shown elsewhere [14].

The topology of the obtained thick films was investigated using 3D-profilograph Rodenstock RM600. The electrical resistance of thermistor thick films was measured using temperature chambers MINI SABZERO, model MC-71 and HPS 222. The temperature constant B25/85 for these thick films was calculated according to the Eq.[1]:

B25/85 = 2,3026 • log (R-J. Ti-T., (1)

where Rj and R2 were corresponding resistance at T = 25 °C and T2 = 85 °C, accordingly.

The humidity-sensitivity of thick-film elements based on MgAl2O4 ceramics was evaluated on dependence of electrical resistance from relative humidity (RH). The measurements were performed at 20 °C and 1 000 Hz frequency in direction of RH increase and in reverse one.

In respect to the obtained 3D-profilogramph data, the thickness of thick films based on temperature sensitive Cu0,1Ni0,1Co1,6Mn1,2O4 ceramics with p-type of electrical conductivity, Cu0)1Ni08Co02Mn1)9O4 ceramics with w-type of electrical conductivity were 56,16 and 66,67 |am, accordingly. The thickness of thick films based on humidity sensitive dielectric MgAl2O4 ceramics was 52,08 цт

All obtained separate temperature sensitive thick-film elements based on spinel-type NiMn2O4-CuMn2O4-MnCo2O4 ceramics have good electrophysical characteristics. These thick-film elements show exponential temperature dependences of resistances (fig. 1). The values of B25/85 constant were 4 095 and 3 671 K for Cu01Ni01Co16Mn12O4 and Cu0,1Ni0,8Co0,2Mn1,9O4 ceramics, respectively. The both thick films possess good temperature sensitivity in the region from 298 to 358 K. They are distinguished by well-defined profile, but their flatness can be partially lost provided aged pastes were used for

screen-printing. This effect is connected with increasing in the viscosity of the prepared pastes. Therefore, only as-prepared pastes (aged no more a few weeks) should be used to produce high-reliable thick-films elements.

The studied thick-film elements based on d-type MgAl2O4 ceramics possess linear dependence of electrical resistance from relative humidity (RH) in semilogarithmic scale with minimal hysteresis in desorption cycle in the range of RH -60-99 % (see fig. 2). Thus, these thick-film elements are suitable for humidity sensors working in the most important range of RH. These thick films are insensitive to low RH, which can be attributed to bad Ag-Pt contacts between wires and defectiveness of thick film connecting with their viscosity. However, these technological obstacles can be easily removed by modifying screen-print process.

0,1

2,7     2,8     2,9     3,0     3,1     3,2     3,3     3,4 3,5 103/T, K

■—■—[ -

d-type MgAl2O4 thick film

—■— RH increase

 

RH decrease

20     30     40     50     60     70     80     90 100 RH,%

Fig. 1. Typical work characteristics for temperature sensitive thick films based on p-type Cu01Ni01Co16Mn12O4 and n-type Cu01Ni08Co02Mn19O4 ceramics

Fig. 2. Typical work characteristics for thick film based on MgAl2O4 ceramics

Since all investigated separate components (p-, n- and d-type thick films) are of the same chemical type (spinel-like) and possess high temperature/humidity sensitivities, they will be positively distinguished not only by wider functionality (simultaneous temperature-humidity sensing), but also unique functional reliability and stability. To prepare such multifunctional temperature/humidity sensitive elements, we can use typical design performance in respect to the scheme shown in fig. 3. In the case under consideration, the main advantages proper to bulk transition-metal manganite ceramics (wide range of electrical resistance with high temperature sensitivity) and humidity-sensitive MgAl2O4 ceramics will be transformed into thick-film multilayers, resulting in a principally new and more stretched functionality. The spinel-type Cu01Ni01Mn12Co16O4 compound with p-type of electrical conductivity (yellow-distinguished), Cu0,1Ni0,8Mn1,9Co0,2O4 compound with n-type of electrical conductivity and dielectric magnesium aluminate d-MgAl2O4 will be designed as overall integrated structure shown in the topological scheme at right. It should be noted that only three levels of basic spinels (p-, n- and d-type) should be interconnected by four commutation levels to achieve the final temperature-humidity sensing functionality.

0

1000

E sz

о

2

E

о

2

100

a.

10

Side cross section

H - right commutation H - left commutation

Fig. 3. Topological scheme illustrating integrated humidity/temperature sensing in spinel-type multilayer structures

Within proposed configuration (see fig. 3), a several simultaneous functions will be available via resistance measurements between different points of this multifunctional element: p-type thick-film element will be used as in-rush current limiter and temperature sensors utilizing current-voltage dependence of thick-film p-n junction, n-type thick film element will be used as temperature sensor and humidity sensor utilizing thick-film capacitor p-d-n with water-sensitive dielectric layer d.

The separate temperature and humidity sensitive thick-film elements based on spinel-type NiMn2O4-CuMn2O4-MnCo2O4 manganites with p- and n-types of electrical conductivity and dielectric magnesium aluminate MgAl2O4 were prepared using ecological glass constituents. These thick-film elements can be used as starting components to produce multifunctional integrated temperature/humidity sensors for effective environment monitoring and control.

The authors acknowledge support from Internationales Buro des BMBF within BMBF-WTZ Project No UKR 06/006.

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10. Huang J. Preparation and characteristic of the thermistor materials in the thick-film integrated temperature-humidity sensor // Mat. Sci. Eng. 2003. Vol. B 99. P. 523­526.

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БАГАТОФУНКЦІОНАЛЬНА ШПІНЕЛЬНА КЕРАМІКА ДЛЯ СЕНСОРІВ НАВКОЛИШНЬОГО СЕРЕДОВИЩА

Г. Клим12, І. Гадзаман1, О. Шпотюк1, М. Бруннер3, В. Балицька1,4

'Науково-виробниче підприємство "Карат " вул. Стрийська 202, 7903' Львів, Україна 2Національний університет "Львівська політехніка " вул. Бандери '2, 79013 Львів, Україна 3Вища Фахова Школа Кьольну /Університет Прикладних Наук вул. Бецдорфе 2, 50679 Кьольн, Німеччина 4Державний університет безпеки життєдіяльності вул. Клепарівська 35, 79007 Львів, Україна

Отримано температурно та вологочутливі товстоплівкові елементи на основі шпінельної кераміки NiMn2O4-CuMn2O4-MnCo2O4 з p- та n-типами електричної провідності і діелектричної кераміки MgAl2O4. Показано, що такі елементи моя^ть успішно використовуватися як інтегровані температурно/вологочутливі сенсори навколишнього середовища.

Ключові слова: шпінель, товста плівка, сенсор, багатошарова структура.

МНОГОФУНКЦИОНАЛЬНАЯ ШПИНЕЛЬНАЯ КЕРАМИКА ДЛЯ СЕНСОРОВ ОКРУЖАЮЩЕЙ СРЕДЫ

Г. Клим1,2, И. Гадзаман1, О. Шпотюк1, М. Бруннер3, В. Балицкая1,4

'Научно-производственное предприятие " Карат" ул. Стрыйская 202, 7903' Львов, Украина 2Национальний университет " Львовская политехника" ул. Бандеры '2, 79013 Львов, Украина 3Вищая профессиональная школа Кельна. Университет прикладных наук ул. Бецдорфе 2, 50679 Кельн, Германия 4Государственный университет безопасности жизнедеятельности ул. Клепаривска 35, 79007 Львов, Украина

Получены температурно и влагочувствительные толстопленочные элементы на основе шпинельной керамики NiMn2O4-CuMn2O4-MnCo2O4 из p- и n-типов электрической проводимости и диэлектрической керамики MgAl2O4. Показано, что такие элементы могут успешно использоваться как интегрированые температурно/влагочувствительные сенсоры окружающей среды.

Ключевые слова: шпинель, толстая пленка, сенсор, многослойная структура.

Стаття надійшла до редколегії 04.06.2008 Прийнята до друку 25.03.2009

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